MIPS: DTS: CI20: fix interrupt for pcf8563 RTC

Interrupts should not be specified by interrupt line but by
gpio parent and reference.

Fixes: 73f2b940 ("MIPS: CI20: DTS: Add I2C nodes")
Cc: stable@vger.kernel.org
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>